Mono-1-olefins (α-olefins), including ethylene, can be polymerized with catalyst compositions employing titanium, zirconium, vanadium, chromium or other metals, impregnated on a variety of support materials, often in the presence of cocatalysts. These catalyst compositions may be useful for both homopolymerization of ethylene, as well as copolymerization of ethylene with comonomers such as propylene, 1-butene, 1-hexene, or other higher α-olefins. Therefore, there exists a constant search to develop new olefin polymerization catalysts, catalyst activation processes, and methods of making and using catalysts that will provide enhanced catalytic activities and polymeric materials tailored to specific end uses.
One type of catalyst system consists of metallocene compounds contacted with methyl aluminoxane to form a polymerization catalyst. However, in order to achieve the desired high polymerization activities, large amounts of expensive methyl aluminoxane are necessary to form the active metallocene catalysts. This feature has been an impediment to the commercialization of metallocene catalyst systems. Therefore improvements in catalyst compositions and in methods of making the catalyst are needed to afford the desired high polymerization activities at reasonable commercial costs.